Color development process using aromatic hydrazines



reducible silver salts.

Patented Jan. 11, 1944 UNITED STATES PATENT OFFICE COLORADEVELOPMENT raooass USING AROMATIC nrnaazmss David W. Woodward and David M. McQueen, Wilmington, Del., assignors, by mesne assignments, to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application October 16, 1939, Serial No. 299,760

is Claims. (01. 95-88) This invention relates to photography and more particularly to color photography, and still more particularly to color development processes for photographic elements. In a more limited sense it relates to the production of dye images in photographic elements utilizing aromatic hydrazines as'developing agents.

This invention has for an object the production of photographic images in color. A further object is to provide a process for producing color images of improved fastness to light. A still further object is to provide a process for providing stable color images which -are not affected by the products produced in the hydrolysisof film base or photographic layers. A still further object is to produce azo dyes during the' development of photographic films containing A still further object is to provide a new reversal process of developing in which aromatic hydrazines react under conditions of development with a coupling component at the point of the silver salt images to produce azo dyes in situ with metallic silver. Still other objects will appear hereinafter.

One important aspect of theinvention involves the treatment of bleached silver images and residual silver salt images. It has been layers, e. g. gelatino silver halide emulsion layers, are used. In this latter embodiment of the invention a plurality of emulsion layers sensitized to approximately one third of the visible spectrum is used. Thus, a multilayer film composed of three silver halide emulsion layers which are difierentially sensitized are provided with non-migratoryazo coupling components which form dyes upon development complementary in color to the sensitivity of the respective layers.

In each of the embodiments of the invention, the hydrazine is apparently oxidized during the reduction of the silver images to an intermediate which reacts with a coupling component to form an azo dye.

The mild oxidizing agents may be used with soluble or non-migratory coupling components.

found that the hydrazines are not sufficiently 7 active in many instances to develop exposed or In another important embodiment of the invention developing baths containing mildoxidizing agents and hydrazines are used in the development procedures. It has been found that the coupling velocity and dye density are. increased by such procedures.

According to one aspect of the invention, dye coupling components which are soluble in or can. readily be dispersed in developer solutions are used in conjunction with aromatic hydrazines. In another aspect of the invention, dye coupling components which are non-migratory and non-leachable from photographic emulsion It hasaromatic hydrazines.

It is well known in the'art that phenylhydrazine may be oxidized under certain conditions either to phenol or benzene diazonium chloride by certain inorganic salts ,(Richters Organic Chemistry, Vol. II (1929) p. 150). Although the action of silver salts on phenylhydrazine is apparently not known, it is possible that one of these reactions would occur during development of photographic films containing silver salts with It has been found that a certain selected group of hydrazines which can be readily ascertained by a simple testgive good results and form preferred reducing agents. These hydrazines react with readily reducible silver salts to give intermediates that couple with certain aromatic phenols, amines, and. active methylene compounds to give azo dyes. The hydrazines are in general free from negative groups such as sulionic acid orsulfonate groups and carboxylic acid or carboxylate groups. Suitable hydrazines may be determined by a test as follows: An ammoniacal silver nitrate solution is prepared by dissolving one part of silver nitrate in 200 parts of water and adding concentrated ammonia water until the first formed precipitate has just dissolved. Fifty parts of concentrated ammonia water is then added and the total solution made up to 1000 parts with distilled water. To 10 parts of this solution at 20 C. is added one part of a 1% solution of the aromatic hydrazine to be tested. black metallic silver is deposited, the hydrazine is suitable for use in this process, but-if there is no silver deposited at this point, the hydrazine is inoperable in this process.

Such hydrazines as selected by the above detailed test may be used as photographic color If during 30 seconds.

developers in alkaline baths of the.usual type for they are oxidized directly by the more readily reducible silver salts. However, they are preferably used as stated above with reverse, bleached or non-exposed silver salt images and/or in conjunction with mild. oxidizing agents, 0. g. hydrogen peroxides, persulfates, hypoehlorites, and the like. The intermediate roducts produced by these treatments apparently readily form coupling dlazonium compounds.

These active diazo compounds form azo dyes in the presence of suitable coupling components such as are known in the dye chemistry art (see Fierz-David, Kunstliche organische Farbstofi, pp. 87-204). Such coupling components are in general aromatic in nature and possess any one of a number of difierent substituents such as phenolic liydroxyl, alkcxy, amine, alkylamine and arylamine with replaceable hydrogen atoms or groups in the ortho and/or para position to them, or they may be such reactive methylene groups as are known to enter the coupling reaction. The aromatic hydrazines in such developing solutions are solubilized according to the method described in application Serial No. 299,762 James E. Kirby, filed upon October 16, 1939, entitled Developer solutions now U. S. P. 2,220,929. Suitable solubilizing agents include the water-soluble alkali metal, ammonium and amine salts of stearic, palmitic, oleoic, arachidic, oleostearic, ricinoleic, 12-hydroxystearic, myristic, linoleic acid, the same salts of primary or secondary aliphatic hydrocarbon sulfonic acids containing at least 8 carbon atoms, e. g. of dodecane, tetradecane,

octadecane, and 3,10-diethyltridecane-sulfonic acids, mineral oil sulfonates, etc.; the alkali metal, ammonium and amine salts of alkylated aromatic sulfonic acids, e. g. containing a carbon chain of at least 8 carbon atoms, p-dodecylphenolsulfonic, oleo panisidinesulfonic, etc. acids, alkyl sulfates of 8 to 24 carbon atoms, .e. g. dodecyl-, tetradecyl, and octadecyl-sulfate, etc., oleyl sulfate, diethyl cyclohexylamine dodecyl-sulfate, etc. As examples of suitable salt-forming groups, mention is made of sodium, potassium, ammonium, alkylolamine, e. g. mono-,diand tri-ethanolamine, methyl and ethyl amines, etc. Reaction products of long chain carboxylic acids with taurine, isethionic acid, etc. are also useful.

As examples of suitable betaine compounds which may be used are C-(I'l-hGXfidGCYl-abetaine, C-(n-dodecyl)-a-betaine, and the salts of the corresponding open chain betaine compounds. Mixtures of the above agents may be also used. These developing solutions may vary from weakly acid to moderately basic in nature,

i. e., from about pH values 6 to 12, depending upon the choice of hydrazine and coupling component. Alkaline solutions, however, are preferred. Solutions of these pH values may be obtained by any of the customary methods used in organic chemistry and they may contain any of the following or closely related types of compounds: weak organic acids such as acetic and the like; salts such as alkaline carbonates, phosphates, acetates, phthalates, cltrates, borates and the like, or alkali hydroxides.

There are two procedures which may be used in preparing azo dye images by this process. One consists in adding to the hydrazine developing solution a soluble coupling component which will be converted bythe diazo compound produced on development to an insoluble azo dye at the point of development. To produce a negative image in azo dyes a film bearing a bleached negative silver image is introduced into a developing solution as described above and after development the silver and silver salts are removed by any standard method, e: g., as by Farmers reducer. To produce a positive or reverse image in azo dyes, the film is exposed and given a preliminary development in a non-color forming developer e. g. Metol-hydroquinone. The film is then processed with the hydrazine type of developer as described above. Also, a film containing a positive or negative silver image may be bleached to redevelopable silver salts, as, for example, with potassium ferricyanide, copper chloride or copper bromide in the presence of an oxidizing agent such as chromic acid, potassium i'errieyanide in the presence of alkali carbonate or ammonia, etc., and then re-developed in such a color-forming developer as described above. In all cases a film is obtained bearing a clear, bright azo dye image in which the dye has been deposited at the point of reduction of the silver salts and proportional to the amount of silver salt reduced.

Another method for producing films containing azo dye images by this same process as mentioned above, consists in using films in which a nonmigratory coupling component has been incorporated in the emulsion. These are coupling components which, on account of their chemical constitution or molecular size, remain firmly bound in gelatin films and are not leached from them nor migrate in them when the films are placed in the customary baths used in color photography.

.The speed of development by the hydrazine solutions may be controlled if desired by the addition of ammonia, which slows the reaction considerably. Thus the addition of about 1% of concentrated ammonia water, for instance, will about double the time of development.

By choice of suitable coupling compounds, it is possible to secure a most complete color range of azo, dyes; thus phenols and active methylene compounds will produce yellow to orange dyes. Naphthols will produce colors ranging from redorange through red to purple, and certain phenylenediamines, aminophenol, and aminonaphthol derivatives will yield colors ranging from blue to blue-green. We are not limited by such classification, however, as these and many other combinations producing azo dyes and well-known in azo dye chemistry (see Fierz- David) are applicable. Nor are we limited to monoazo dyes for by either the use of a difunctional hydrazine as a developing agent or a coupling component containing an azo group or both, it is possible to prepare films containing bis tris-, or tetra-kis azo dyes.

The invention will be further illustrated but is not intended to be limited by the following examples, wherein the parts stated are parts by weight:

Example I A photographic film containing a light-sensitive silver halide-gelatin emulsion is exposed and developed in a Metol-hydroquinone developer.

. The film is then washed, re-exposed to light, and

processed in a bath prepared by adding to a mixture of parts of water and 5 parts of 2% sodium o1eate,2 parts of phenyl hydrazine, 2 parts of sodium carbonate and 1 part of sodium betabright orange azodye image.

I naphtholate, at a temperature of about 8' 0.,

for a period of 10 to minutes. After development the film is thoroughly washed and placed in a 4% solution of potassium ferricyanlde i'or five minutes, washed, and placed in 25% sodium thiosulfate for five minutes, then thoroughly washed. The resulting film contains a clear The dye has the following probable structure:

, N=N C .11.

Example II In an experiment similar to that described in Example I and using the sodium salt 01' acetoacetanilide, prepared by dissolving 1 part of acetoacetanilide in 5 parts of 2% sodium hydroxide solution, a film was obtained bearing a transparent yellow azo dye image.

Example III In experiments similar to those described under Example I, the phenylhydrazine is replaced by an equal amount of 0-,mor p-tolylhydrazine. The resulting films are similar in appearance to those described in Example I. The azo dyes have the following probable structure:

Ewample IV In experiments similar to those described under Example II, the phenylhydraz'ine was replaced by o-, mor p-tolylhydrazine. The resulting films are similar in appearance to those described in Example II. The azo dyes have the following probable structure:

0 0- on: mucodn-N=No,H.om

Exampf V In an experiment similar to those described in Examples I, the phenylhydrazine is replaced by 10 cc. of p-nitrophenylhydrazine hydrochloride solution containing 1.5 parts per 100 parts of water. The-resulting films contain bright red azo dye images. The dye has thefollowing probable structure:

Alex cum 0,- p

A developing solution is prepared by dissolving 0.5 part of p-nitrophenylhydrazine hydrochloride in parts of water to which is added 8 parts of 2% sodium oleate solution, 5 grams otsodium acetate, 1 part 01' acetic acid and 1 part or 1- dimethylamino-5-naphthol. This developing solution is used in experiments similar to those described inExample I. The resulting films contain transparent images of blue azo dyes 01' the following probable structure:

INCH:

H N=N--c.mNo,

Example VIII In experiments similar to that described in Examples I, II and VII, the hydrazine thereof is replaced by p-hydrazinodiphenyl. In these cases films containing red, yellow, and blue azo dye images, respectively, orthe following structure were obtained:

ArN=NCeH4C cH5p Example IX 'In experiments similar to those described under Examples I and II, p-bromophenylhydrazine was used as the developing agent. The resulting films contained, respectively, red and yellow dye images. These dyes have the following probable structures:

Example. X

In experiments similar to those described under Examples I, III and V-, the sodium betanaphtholate is replaced by the sodium salt of 2-hydroxy-3-naphthoic acid anilide. The resulting films contain bright red azo dye images and these dyes have the'following probable structures:

Example XI In a seriesof experiments similar to those described under Examples I, III and V, the sodium beta-naphtholate was replaced by an equal amount of o-chloro-acetoacetanilide. .The re-' sulting azo dye images were greener than those obtained with acetoacetanilide. These dye having the following probable structures:

In a series of experiments similar to those described in Examples I, III and V, the sodium [1- naphtholate was replaced by ;dichloroacetoacet anilide. The resulting yellow azo dye images were slightly greener in shade and have the following probable structure:

In a series of experiments similar to those described in Examples 1, III and V, the sodium [1 naphtholate was replaced by 1-phenyl-3-methyl- Example XV A photographic emulsion containing .silver halide and stearoyl-J-acid in the ratio of 10 to 1 was coated on a cellulose acetate base, exposed and developed in a non-color-forming developer such as Metol-hydroquinone, then re-exposed and processed in a solution made as follows: Two parts of phenylhydrazine is dissolved in a mixture of 90 parts of water and 8 parts 'of 2% sodium oleate solution, and to this is added 2 grams of sodium carbonate. After development for 15 minutes at 8 C., the film is washed, the silver bleached as in potassium ferricyanide solution and the silver salts removed with sodium thiosulfate. The resulting film contains a bright orange-red azo dyestuff image. This dye has the following probable structure:

Im srvncvowmnaom l on Example XVI In experiments similar to that described under Example XV, the phenylhydrazine is replaced by.

-, m-, or p-tolylhydrazine in equal amounts. The resulting films appear similar to those described under Example XV. The azo dyes have the following probable structure: I l

In experiments similar to that described under Example XV, the phenylhydrazine is replaced by p-bromo-phenylhydrazine in equal amounts. The resulting films appear similar to those produced in Example XV, and the azo dye has the following probable structure:

Example XVIII In experiments similar to that described under Example XV, the phenylhydrazine was replaced by an equal amount of p-nitrophenylhydrazine. The resulting film contained bright magenta dye images. This dye has the following probable structure:

Example XIX In experiments similar to that described under Example XV, the phenylhydrazine was replaced by p-hydrazino-diphenyl. The resulting films contained magneta dye images. This dye has the following probable structure:

Example XX A photographic emulsion containing 1 part of p-dodecylacetoacetanilide to 10 parts of silver halide is coated on cellulose acetate film base and treated as the films in Example XV to XIX, inclusive. The films all contained yellow to orange azo dyes. These dyes have the following probable structure:

(JO-C11:

In place of the films used in any of the preceding examples, it is possible to use films pre pared by removing the silver image, after the first development, with a reversal bath such as one containing chromic acid or sulfuric acid and a dichromate, and the like, and then reducing the remaining silver salts and reoxidizing them with a ferricyanide, an acid chromate, or a copper halide, to silver salts which are more readily reducible by the hydrazines. Similarly, if the films used in any of the preceding examples are exposed to light through films bearing negative images, they may be developed in a Metol-hydroquinone developer, and then fixed and the silver reoxldized according to the method of the preceding sentence and then color developed as described'in the preceding examples to yield images in azo dyes.

Example XXI To a mixture of parts of water and 5 parts of 2% sodium oleate solution is added 2 parts of phenylhydrazine, 2 parts of sodium carbonate, and. 1 part of sodium beta-naphtholate. A photographic film containing a light-sensitive silverhalide-gelatin emulsion layer is exposed and developed in this bath at 8 C. The development requires about ten to fifteen minutes. After development the film i thoroughly washed and placed in a 4% solution of potassium ferricyanide for five minutes, washed, and placed in 25% sodium thiosulfate for five minutes. then thoroughly washed. The resulting film contains a aaaaaia 489,274, 489,093, 483,000 and French Patents clear bright orange azo dye image- The the following probable structure:

I N =NCaHs dye has The reduction of silver salts by aromatic amino compounds is believed to proceed withoxidation of the amine group to a nitroso group or a group readily convertible to the same, for in the development of silver salts with p-aminodiethylaniline in the presence of phenol an indoaniline dye is produced the structure of which indicates that it is derived from p-nitrosodiethylaniline and phenol. In the case of phenylhydrazine, if the reaction proceeds in the same manner, the product might be expected to be phenylnitrosoamine. The aromatic nitrosoamines are known to be in tautomeric equilibrium with the diazo compounds,

which will couple with aromatic phenols, amines and active methylene compounds to produce azo dyes. That the reaction occurs in some such manner as this seems likely, since development of silver salts with phenylhydrazine in the presence of beta-naphthol yields the same azo dye as produced from the benzene diazonium compound and beta-naphthol.

In' place of the specific aromatic hydrazines of each of the respective examples may be substituted other aromatic hydrazines which have developing powers andare capable of reducing silver salts to metallic silver. Suitable reducing or developer baths are described in U. S. P. 2,220,929. Among the useful primary aromatic hydrazines are Tolylhydrazines Nitrophenylhydrazines Bromophenylhydrazines Chlorophenylhydrazines Chloronaphthylhydrazines Bromonaphthyihydrazines p-Diphenylhydrazines p,p-Diphenyldihydrazines Alpha-naphthylhydrazines Beta-naphthylhydrazines A small amount of a mild oxidizing agent may be used in each of the developing processes described above. In general amounts up to 2% give satisfactory results. Suitable oxidizing agents, in addition to those recited above include alkalimetal peroxides, perborates, percarbonates, alkali metal salts of perorganic acids, e. g. peracetic acid, perpropionic acid, etc.

The invention is not limited to the treatment" of ferrocyanide bleached images: on the contrary silver salt images such as silver chloride, silver bromide, silver chloro-bromide, silver iodide, silver ferricyanide, and the complex silver copper 830,878 and 830,926.

The color development procedures hereof are. furthermore, not limited to any specific type of photographic element. 'Thus, they are applicable to photographic films and plates bearing a single emulsion layer or to multilayer photographic elements. Thus, mono-, biand tri-packs may be processed. In the case of such multilayer films and plates, the azo coupling components are chosen so that they form dyes upon treatment with the hydrazine reducing baths hereof, which dyes are complementary in color to the utilized sensitivity range of the respective emulsion layer in which they are incorporated. Upon exposure to a natural color scene, such film can be developed in a non-color-forming developer and,

without removing the thus formed silver images or re-exposing, the residual silver salts can be reduced with one of the hydrazine solutions hereof. Upon removal of all of the silver images, a

a positive transparency in natural colors is formed.

The invention is also useful with stripping films whereby the emulsion layers are releasably attached to a photographic element support which may be paper or a cellulosic ester or ether film base or a resin. The sensitive emulsion of such films is coated onto a thin menstruum of collodion which in turn has' been coated onto a water soluble adhesive layer such as glue or dextrine which in its turn has been coated onto a suitably prepared temporary support of the type.

previously described. The adhesive layers. may

i be of the type which is softened or dissolved in v.veloped in the hydrazine developers hereof con-' taining the proper and desired coupling component. The color development processes hereof constitute a distinct advance to this art because the previously available toning method lack brilliancy and the transparency of dye images.

This invention has the advantage that, while the processing of the films is fully as simple as in the previously discovered processes of color development, the colors produced are more-stable. Azo dyes as a class are known to be much more stable than those used in the other processes, and it is possible to obtain a much wider range of colors, thus approximating more nearly the ideal colors for a perfect three-color subtractive process. This process then has all of the advantages of the former process without many of its disadvantages such as short life of the film and failure to reproduce natural colors faithfully.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not intend to limit myself to the specific embodiments herein except as definedby the appended claims.

We claim:

1. In a photographic reversal process the step 1 of developing the reversed silver salt image in a developing solution containing as the sole type of reducing agent an aromatic hydrazine, in the presence of an azo coupling component.

- 2. In a photographic reversal process comprising exposure of a photographic element containing silver salts to an image, development in a non-color forming photographic developer, reexposure to light and re-development, the step of developing the reversed image in a developing solution containing as the sole type of reducing agent an aromatic-hydrazine, in the presence of an azo coupling component.

3. The method of producing a direct positive by a reversal process which comprises exposing an emulsion layer containing light sensitive silver salts, developing said layer in a non-colorforming photographic developer and reducing the residual image in a developing solution containing as the SOle type of reducing agent an aromatic hydrazine, in the presence of an azo coupling component, and removing the silver images.

4. The process which comprises developing a bleached silver salt image in a developing solution containing as the sole type of reducing agent an aromatic hydrazine, in the presence of a coupling component to form a dye.

5. The process which comprises developing a bleached silver salt image in a developing solution containing as the sole type of reducing agent an aromatic hydrazine, in' the presence of an azo coupling component to form an azo dye image.

6. A process which comprises developing a photographic element having at least one layer con- 11. In a photographic reversal process the step of developingthe reversed silver salt image in a developing solution containing as the sole type of organic reducing agent a primary aromatic hydrazine characterized by its ability to precipitate silver from an ammoniacal solution containing approximately 0.1% ct silver nitrate in seconds at 20 C. in the presence of an azo coupling component to form a dye image.

12. A process 'which comprises developing a silver ferrocyanideimage in a developing solution containing as the sole type of organic reducing agent an aromatic hydrazine in the presence of an azo coupling component to form an azo dye image.

13. The method of producing a direct positive by a reversal proces which comprises exposing a photographic element bearing an emulsion layer containing light sensitive silver salts and a non-migratory azo coupling component, developing said layer in a non-color forming photographic developer and reducing the residualsilver salt image in a developing solution containing as the sole type of organic reducing agent an aromatic hydrazine, and removing the silver and silver salts.

14. A process which comprises developing a photographic element containing a silver salt image in an aqueous developer solution containing as the'sole type of reducing agent an arcmatic hydrazine dissolved in an aqueous solution containing not more than 1% of a long chain surface active polar compoundcontaining a hydrophilic group and a hydrophobic group of at least 8 carbon atoms in the presence of a coupling component to form a dye.

15. A process which comprises developing a photographic element containing a silver salt image in. a developing solution containing as the sole type of reducing agent monophenylhydrazine and an azo coupling component containing 8. An aqueous alkaline developersolution conducing agent a primary aromatic hydrazine characterized by its ability to precipitate silver from anammoniacal solution containing approximately 0.1% of silver nitrate in 30 seconds at 20 C. in the presence of an azo coupling component to form a dye.

10. A process which comprises developing a photographic element containing a silver salt image in a developing solution containing as the sole type of organic reducing agent a primary aromatic hydrazine characterized by its ability to precipitate silver from an ammoniacal solution containing approximately 0.1% of silver nitrate in 30 seconds at 20 C; in the presence of an azo coupling component to form a dye.

a phenolic group to form an azo dye image.

16. A process'which comprises developing a photographic element containing a silver salt image in a developing solution containing as the sole type of reducing agent para-nitrophenyl hydrazine and an azo coupling component containing a reactive methylene group to form an azo dye image.

1'7. A process which comprises developing a photographic element containing a silver salt image in a' developing solution containing as the sole type of reducing agent para, para'-diphenyldihydrazine and an azo coupling component, containing aromatic amino groups to form a dye image.

18. A process which comprises developing a photographic element containing a silver salt image in a developing solution containing as the sole type of reducing agent an aromatic hydrazine dissolved in an aqueous solution containing not more than 1% of sodium oleate in the presence of an azo coupling component to form an azo dye image. DAVID W. WOODWARD.

DAVID M. MCQUEEN, 

